#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    vector<ll> V(100);
    V[0] = 1;V[1] = 1;
    rep(i,2,100){
        V[i] = V[i-1] + V[i-2];
    }
    int N;
    cin >> N;
    cout << V[N] << endl;
}